Oven heat control



March 10, 1942. T. A. WETZEL OVEN HEAT CONTROL Filed April 9, 1938 6 ,0 M/LWW a w W wk m u J p Z 0 w Z a M U m 0 w QM m r m, L fiw/ Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE 2,275,651 OVEN'HEAT common Theodore A.

Milwaukee Wetzel, Mil Gas Specia waukee, lty Company, Milwaukee,

Wis, assignor to Wis., a corporation of Wiscons Application April 9, 1938, Serial No. 201,085

1 Claim.

This invention to control mechanism and is more particularly concerned A feature of this invention is the provision of control ing mechanism, especially arranged for thermal relation with either the pilot the main burner of the gas range. It is a further feature of this invention to provide hermetically sealed electrical contacts of the non-liquid an ignition circuit in the'gas range or other appliance. Another feature or other fuel can flow to the system.

These and other objects tion with the accompanying drawing illustrating the preferred physical embodiments of the invention.

In the drawing: 7

Figure 1 is a view showing a domestic gas range incorporating the principles of the present inventlon; and t Figure 2 is a detail sectionalview of the therostatically responsive switch associated with the burners as shown in Figure 1.

While I shall describe my invention as incorporated in controlling open top or grate burners 2 of usual construction and an oven compartment indicated in its enburner is under the control of an oven thermostat 12, which includes an adjustable valve 13 and suitable thermostatically controlled mechanism that includes a thermostatic bulb 15 located in the upper part of the oven 3. The control of the gas flow may be adjusted by suitable mechanism that includes a knob 11 disposed at the front of therange I.

Referring now to Figure 2, a thermal switch unit 3| is enclosed in a sealed casing 10, within which are mounted contact member 65, 66 and 61. .The members and 61 have contacts 12 the contacts 15 and 13 on the member 66 and 61 are in engagement and the contacts 12 and 14 on the members 65 and, are out of engagement.

In Figure 1 stand-by disposed at a position adjacent the control valve 12. The thermostat switch 3| is mounted adjacent the pilot 8| in a constant flame of the latter impinges on the shield or casing thereof.

The thermostatic switch 31 is includes two coils 81 and 88, both acting on a plunger 911 that controls a valve 91 which, in turn, contfols the flow of gas to both the main burner 6 and the pilot burner 81.

connected to a fixed part, as at 92 on the housing 93 and is disposed between a pair of spring contacts 94 and 95 having contact disposed/within the housing 93 in a position to affect the bimetallic element 92. Normally, when the element 92 is cold, it moves to a position holding the spring member 94 with its contact 91 out of engagement with the contact 98 on the other member 95, but the latter is held against upward movement by a fixed stop I88. Thus, when no current flows through the resistance element I82, the thermostat 92 is cold and the contacts 91 and 98 are open.

The oven control switch 58 is connected by a conductor 8 to one side of the transformer T. The other end of the latter is connected by a conductor III to the fixed end 2 of the spring member 94, and at this point the intermediate conductor 58 of the unit 3| is also connected. The conductor 59 of the unit 3| is connected to one side of the ignition coil 85, and another conductor 5 connects the other end of the ignition coil 85 to one end of the resistance unit I82. The other end of the latter is connected by a conductor I I8 to the oven switch 58, and at an intermediate point the conductor I I8 is connected by means of a conductor H8 to the adjacent ends of both of the coils 81 and 88. The other end of the first coil 81 is connected to the lead 51 of the unit 3|, and the other end of the coil 88 is connected by a conductor I I9 to the outer end of the other spring member 95, as at |2|, of the unit 88.

The electric shut-off valve 52 is so constructed that the coil 88 can exert sufficient pull to raise the valve 9| into its open position, permitting gas to flow from the main 8 to the control unit I2, but the coil 81 is constructed so that it fs capable: only of holding the valve 9| open provided the valve is already in its open position when the coil 81 is energized, but the coil 81 is not capable of exerting sufficient pull to open the valve if it should be closed when the coil 81 is energized.

The operation of the electrical ignition system in which the unit 9| is incorporated, accordin to the principles of the present invention, is substantially as follows:

When it is desired to turn on the oven of the range I, the oven switch 58 is closed. Current then flows from one side of the secondary of the transformer T through the conductor II8, the closed switch 58, the conductor 8, the heating resistance I82, the conductor II5, the ignition coil 85, the lead 59, the member 81 (Figure 2) the engaged contacts 13, (since the unit 9| is cold), the member 88, the lead 58, and the conductor I I I back to the other side of the secondary of the transformer T. This flow of current heats the ignition coil 85 and the resistance coil I82, and heat from the latter affects the thermostat 92 so that after a short period of time it bends downwardly and permits the contact 91 on the spring member 94 to engage the contact 98 on the other spring member 95. As soon as the contacts 91 and 98 are engaged current flows from one side of the secondary .of the transformer T through the conductor II8, the closed switch 58, the conductor II8, the solenoid coil 88, the conductor II9, the spring member 95, the engaged contacts 98 and 91, the spring member 98, and the conductor I back to the other side of the transformer. This flow of current energizes the solenoid coil 88 and opens the valve 9 I, permitting gas to flow from the main 8 to the, inlet connection I8 and the regulating valve I2 to the main gas burner 8. Since at this time the ignition coil 85 is hot, gas flowing out of the burner 8 normally is ignited and the burner flame in turn ignites the flame from the pilot flow of gas to the stand-by pilot 8|. The pilot burner 8| then heats the unit 8| causing thermostat 11 to engage the contact 18 with the contact 12 and then disengage the contact 15 from the contact 19. This interrupts the current flowing through the ignition coil and the heating coil I82, and energizes the holding solenoid coil 81 through the following circuit: From one side of the secondary of the transformer T through the conductor 8, the closed switch 58, the conductor II8, the coil 81, the lead 51, the member 85, the engaged contacts 12 and 14, the member 88, the lead 58, and the conductor II I back to the other side of the transformer. Since current through the resistance I82 is interrupted the element 9| cools and returns to a position separating the contacts 91 and 98, whereupon the coil 88 is deenergized.

In the event, however, that after the initial energization of the circuit, including the ignition coil 85, the heating coil I82 and the solenoid coil 88, the main burner 8 or the pilot 8| does not ignite, then the unit 3| remains in its cold position and current continues to flow through the first-mentioned circuit above. The continued flow of current'through the heating coil I82 continues to heat the thermostat 92 so that the thermostat 92 will be bent downwardly and will eventually leave the spring member 94 against the stop I84 and will move the lower spring member 95 away from the stop I84 and disengage the contacts 91 and 98. As soon as this disengagement occurs the current through the solenoid opening coil 88 is interrupted and the shut-off valve 9| automatically returns to a closed position, even though the oven switch 58 should be left closed. Thus, the user will know from the fact that the burner does not ignite that something is wrong with the system, but the automatic closing of the shut-off valve prevents filling the oven with unburned combustible gas.

Another advantage of this arrangement is that there is no constantly burning pilot flame, with attendant possibility that the pilot might go out and fill the space with combustible gas. As soon as the oven switch is closed, the ignition coil is heated, but if the burner does not light thenthe system automatically closes the shut-off valve so that only a very small quantity of gas flows into the zone during the time that the shut-off valve was temporarily opened to provide an opportunity for the burner to become lighted. In a similar way, if the pilot 8| does not light, the unit 3| is not energized even though the burner 8 might light. If the stand-by pilot does not light or should go out, then the unit 3| returns to its cold position and the subsequent continued heating of the coil I82 that follows the closin of the cold .contactsin the unit 3| will act through the thermostat or bimetallic element 9| to close the shut-off valve automatically, preventing further gas flow. Also, any interruption of current, as by afailure of the supply, even if only momentary, or a rapid turning off and on. of the oven switch 58, automatically causes the system to shut down, and when the current is restored the system automatically starts a new ignition cycle.-

It will thus be seen that the arrangement shown in Figure 1- employing the sealed or shielded thermostatically controlled contacts of the non-liquid type is so arranged that, without a constantly burning pilot flame and the attendant possibility of going out and filling the space with unburned combustible gas, the oven can be turned on merely by closing the oven control switch 50, which energizes an ignition coil and when the latter is at a temperature sufilcient to ignite gas the shut-off valve is opened to admit gas to the burner, but if for some reason the burner does not light then after a moment or two the gas is automatically turned off and at the same time current to the ignition coil is also automatically interrupted. Also, the oven, when on, can be turned off merely by opening switch 50 which, in the normal operation of the oven control means, is efiective at all times for controlling opening and closing of the shut-01f valve 9|.

While I have described the preferred means in which the principles of the present invention have been embodied, it is to be understood that my invention is not to be limited to the particular details shown and described above, but that, in fact, widely different means'may be employed in the practice of the broader aspects of my invention, within the scope of the appended claim.

What I claim, therefore, and desire to secure by Letters Patent is: v

In combination in oven control means, an oven, a main burner therein, a gas supply line connected to said main burner, a pilot burner adjacent said main burner connected to said line, a normally closed shut-ofi valve in said line in 'advance of said burners, a first solenoid coil effecconnected to the other end of said first opening said valve, a second solenoid coil efiective when energized for holding said valve open but inefieetive for opening it, an ignition coil adjacent said main burner, a transformer, a switch having one side connected to one end of the secondary winding of said transformer, a heating coil connected to the other side of said switch and to one side of said ignition. coil in series, one end of each of said solenoid coils being connected to said other side of said switch, means comprising thermostatic means subject'to' the heat of said burners efl'ective for closing the circult of said ignition coil and opening the circuit of said second solenoid coll when said thermostatic means is cold and openingthe circuit of said ignition coil and closing the circuit of said second solenoid coil when said thermostatic means is hot, when said manually operated switch is closed, a normally open time switch solenoid coil and to said other end of said secondary winding in series therewith, and a thermostat exposed to said heating coil effective for closing said time switch responsive to heating of said heating coil for a predetermined time and for opening said time switch responsive to heating of said heating coil in excess of said predetermined time.

tive when energized for THEODORE WE'IfZEL.

manually operable control' 

